1. Field
The following description relates to a pressure transducer using a ceramic diaphragm, and more particularly, to a pressure transducer using a ceramic diaphragm, which is not easily damaged so that there is no risk of leakage of a target medium to be measured, having a superior mass-production capability and a reduced volume and enabling low-price by simplifying a flexible cable and a printed circuit board (PCB) to connect the transducer and a signal processing chip.
2. Description of the Related Art
Generally, a pressure transducer is used for various fields, such as industrial fields and civil engineering fields, which require a high level of precision to accurately measure a wide range of pressure. The pressure transducer includes strain gages for pressure measurement.
A strain gage may be categorized into an electrical strain gage that electrically measures the strain of an object and a mechanical strain gage that mechanically measures the strain. The electrical strain gage measures a deformation rate of an object from the change of an electrical resistance of the strain gage which is caused when the object deforms. The mechanical strain gage detects a slight change in distances between two points and measures a deformation rate of an object to be measured from the detected distance change. With the introduction of the strain gages, deformation of an object can be precisely measured, and it is possible to estimate stress from the measured deformation.
As the high-tech core technologies have been digitized, diversified and capable of high-performance, there has been a worldwide increasing need for a pressure transducer in various fields, and hence many countries have launched pressure transducer technology development projects as an important high-tech business and provided intensive support to research and development projects, whereby the level of technique has been further increased and the establishment of the mass-production system could be realized. As a result, it is feasible to produce a compact, smart pressure transducer at a lower price.
As a conventional pressure transducer, a pressure transducer using a stainless diaphragm (Korean Patent Registration No. 10-240012) is used. However, because the fabricating processes of the stainless diaphragm for the conventional pressure transducer are complicated and a gage is attached manually, the manufacturing process is complicated and thus the manufacturing costs are increased. In addition, if the gage is exposed to the air or to a medium (liquid or gas) to be measured, it is easy to corrode, which may result in deterioration of long-term stability or reliability of the gage. Further, if a metal thin film strain gage is broken, the entire pressure transducer needs to be replaced, and the stainless diaphragm is not suitable to measure a pressure of a corrosive gas and liquid.
To overcome the aforementioned drawbacks, Korean Laid-Open Patent No. 2001-0105085 discloses a pressure transducer using a ceramic diaphragm that is formed to have thereon a high-resistance thick film or a thin film gage, which is air-tightly sealed by a ceramic cap or coated with a protective layer of a special insulating coating, whereby the pressure transducer can be used for both a gas and liquid and have superior anti-corrosion properties.
However, in a conventional pressure transducer using a ceramic diaphragm as shown in FIG. 5, the ceramic diaphragm 1 is made of ceramic, which may be damaged when excessive pressure is exerted thereon, and thus may cause a serious risk of leakage of a medium to be measured. Especially, if the medium is a toxic gas, the leakage of the medium may result in severe consequences.
In addition, in a case of a pressure transducer using a ceramic diaphragm as shown in FIG. 6, there is a limitation in reducing a gap G for strain gages 2 when mechanically processing a base plate 3. It is almost impossible to fabricate the base plate 3 to have a gap G that is equal to or less than 10 μm. Thus, when the ceramic diaphragm 1 is significantly bent due to an excessive pressure applied thereon, the wide gap G prevents the ceramic diaphragm 1 from contacting the base plate 3, which may lead to the ceramic diaphragm 1 being broken. The broken ceramic diaphragm 1 may result in the leakage of a medium, which is to be measured, through a venting groove.
Moreover, the pressure transducers using a ceramic diaphragm, as shown in FIGS. 5 and 6, use a circular-shaped ceramic diaphragm 1 as shown in FIGS. 7A and 7B, which is not effective for mass-production. Accordingly, the price of the pressure transducer is increased. Furthermore, since flexible cables (not shown) and a printed circuit board (PCB) (not shown) to connect the transducer and a signal processing chip have to be fabricated to fit the shape and size of the circular ceramic diaphragm 1, it causes an increase in volume and cost of the pressure transducer.